1. Field of the Invention
The disclosures herein relate to a touch panel and a method of detecting a position.
2. Description of the Related Art
A touch panel (i.e., touchscreen panel) is an input device that allows input to be made directly on a display screen, and is generally placed in front of the display screen. Touch panels are widely used in various applications because of their capability of allowing direct input based on visual information provided on the display screen.
A resistive-type touch panel and a capacitive-type touch panel are widely known in the art. The resistive-type touch panel includes an upper electrode substrate and a lower electrode substrate having respective transparent conductive films. These substrates are arranged such that the corresponding transparent conductive films face each other. When pressure is applied to a point on the upper electrode substrate, the transparent conductive films are brought into contact with each other, thereby allowing the position of the pressed point to be detected.
The resistive-type touch panel is classified into a four-wire type, a five-wire type, and a diode type. In the four-wire type, an X-axis electrode is disposed on one of the upper electrode substrate and the lower electrode substrate, and a Y-axis electrode is disposed on the other substrate (see Patent Document 1, for example). In the five-wire type, an X-axis electrode and a Y-axis electrode are both disposed on the lower electrode substrate while the upper electrode substrate serves as a probe for detecting voltage (see Patent Document 2, for example). In the diode type, diodes are disposed on the lower electrode substrate. Two electrodes for applying voltage and four electrodes for monitoring a potential are provided, and, also, an electrode serving as a probe for detecting voltage is provided on the upper electrode substrate. This type is also referred to as a seven-wire type because seven electrodes in total are formed (see Patent Document 3, for example).
The capacitive-type touch panel detects an electrical current as the current flows through a transparent electrode or the like in response to a finger or the like coming into the close proximity of the touch panel, thereby detecting the relevant position.
Further, a touch panel in which a resistive-type touch panel and a capacitive-type touch panel are stacked one over another is known, which utilizes respective characteristics of the resistive type and the capacitive type (see Patent Documents 4 and 5, for example).
The capacitive-type touch panel employs a capacitive-coupling-based detection mechanism, and, thus, can detect the position of a point that is touched, even in the absence of pressure being applied. Contact by an insulating object, however, cannot cause its contact position to be detected. The resistive-type touch panel does not require an object coming into contact with the touch panel to be made of any particular type of material. However, certain pressure needs to be applied to the touch panel because position detection is performed based on a physical contact between a transparent conductive film serving as an upper resistive film and a transparent conductive film serving as a lower resistive film.
Patent Documents 4 and 5 disclose a structure in which a capacitive-type touch panel and a resistive-type touch panel are stacked one over another, which have respective advantages of the capacitive-type touch panel and the resistive-type touch panel.
A touch panel having such a structure, however, gives rise to the problem of increased thickness and the problem of increased cost due to the provision of two types of touch panels stacked one over another.
Accordingly, there may be a need for a thin, low cost touch panel that has respective advantages of the capacitive-type touch panel and the resistive-type touch panel, i.e., a thin, low cost touch panel that allows position to be detected only upon a slight touch and that does not require a touching object to be made of a particular material. Further, there may be a need for a method of detecting a position in such a touch panel.    [Patent Document 1] Japanese Patent Application Publication No. 2004-272722    [Patent Document 2] Japanese Patent Application Publication No. 2008-293129    [Patent Document 3] Japanese Patent Application Publication No. 2005-196280    [Patent Document 4] Japanese Utility Model Registration No. 3132106    [Patent Document 5] Japanese Utility Model Registration No. 3139196    [Patent Document 6] Japanese Patent Application Publication No. 2009-116849